The present invention relates to an implantable device, to a process of producing such a device and to the biomedical use of such a device.
U.S. Pat. No. 5,456,723 discloses an implant having a porous metallic surface which has been treated by sandblasting and reductive acid etching resulting in a surface micro-roughness having a maximum peak-to-valley height of about 20 to 30 .mu.m and a roughness spacing of from 0.5 to 10 .mu.m, preferably of about 1-5 .mu.m. The extremely sharp, comb-like structure is necessary in order to achieve sufficient adhesion between the implant and the coating material (hydroxyapatite) formed on it by anchoring the hydroxyapatite in the implant.
A drawback of most hydroxyapatite-coated implants is that the anchoring of hydroxyapatite onto the implant requires high processing temperatures, which limit the choice of substrate materials and result in higher processing costs. The previously preferred technique for coating implant materials with hydroxyapatite is plasma deposition (for a review, see P. Screkian, in Hydroxylapatite Coatings in Orthopaedic Surgery, Ed Geesink and Manley, Raven Press NY, 1993, p. 81-87). Another disadvantage of the plasma deposition technique, in addition to the high temperatures involved, resides in the relatively large particle size, in the order of 30-70 .mu.m.
An aim of the present invention is to provide an implantable device that can be used in a wide variety of biomedical applications (surgery, bone-replacement, prosthodontics etc.), and results in an effective bone formation and can be processed at ambient temperatures.